This invention relates to archery accessory devices, and is more particularly directed to rangefinder bow sights of the type in which a vertical array of sight pins is used to aim the bow, depending on the range to the target.
Conventional sight-pin aiming devices can assist an archer or bow hunter in aiming correctly at a target or game animal. These are effective for level-ground shooting.
When the archer and target are at different elevations a change in the range to the target will produce a change in the angle between the archer and the target. The inclination angle can be used to establish range from a known elevation. It is usually the case in bow hunting for the hunter to establish an elevated position in a tree stand or blind near a game trail, and await the approach of a deer or other game animal. Once the deer comes within range, the hunter will usually have only one opportunity to use his arrow, so the shot must be made to count. Thus, it is highly important that accurate aim be established, taking into account the distance to the deer.
Several rangefinder sights have been proposed, which have both advantages and drawbacks. In one version, a mechanical arrangement of sight pins pivots up and down as the bow is angled to different elevations. However, sights such as this have an undesirable sway about their pivots, which makes accurate sighting difficult. Other versions employ a plurality of light-emitting sight pins, which all light at once, leaving range selection entirely to the archer's judgment. Still another proposed rangefinder sight employs a number of mercury tilt switches which close at a variety of different bow angles and light associated illuminated sight pins as the bow's inclination angle changes. However, mercury switches tend to have rather inexact on/off points so that there is a great deal of uncertainty in aim. This inexactness, and the tendency to light more than one sight pin at a time, places severe limits on shooting accuracy, and renders the device too unreliable to use in many situations.